1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus having a display screen which is segmented into several areas so as to simultaneously display several ultrasonic diagnostic images.
2. Description of the Related Art
There is a conventional ultrasonic diagnostic apparatus with a so-called dual display function. The conventional apparatus includes two frame memories for the display of two ultrasonic diagnostic images; each of these frame memories corresponding to one of the two segments into which the display screen is divided. In this apparatus, for example, B-mode ultrasonic images are sequentially written into a first frame memory, the image being written into the first frame memory is frozen at a given timing, and the B-mode images are written into a second frame memory after the given timing. Therefore, a still picture (frozen image) and a motion picture (live image) are displayed on the screen side by side. In other words, in the conventional dual display ultrasonic diagnostic apparatus, input images are frozen and displayed as a still picture by using the first frame memory and input images are displayed as a motion picture (live image) on a real time basis by using the second frame memory.
On the other hand, with the recent increase in the recording density of data recording medium, it is possible for a large number of diagnostic images for each patient to be recorded. Therefore, the diagnostic images which are displayed on the display screen are written into bulk storage, such as an optical disk device, at the time of diagnosis. The input signal to the display is branched to the bulk storage and written therein in the recording mode. Thus, the images can be recorded without any effect upon the images currently displayed on the dual-display screen.
In the playback mode, the input signal to the display is changed from the one used in the recording mode, that is, the playback image signal is supplied to the display (frame memory) instead of the live image signal from the ultrasonic diagnostic imaging circuit. Since the type of the signal input to the display changes when the mode of the bulk storage changes to the playback mode, the playback signal is supplied to the display after clearing the contents of the respective frame memories.
Therefore, the playback images are frozen and displayed as a still picture by using the first frame memory and the playback images are displayed as a motion picture by using the second frame memory. However, it is not possible to display an image frozen at the time of recording as a still picture and playback images as a motion picture. Namely, the conventional ultrasonic diagnostic apparatus may only be operated in a dual display mode wherein a live picture signal is displayed as a still picture (frozen image) and a motion picture is displayed on another dual display mode wherein a playback signal from the bulk storage is displayed as a still picture is displayed and a motion picture. The prior apparatus is not able to be operated with a dual display mode wherein a live picture signal is displayed as a still picture and a playback signal is displayed as a motion picture, giving rise to inconvenience during diagnosis.